Many of the world's islands were once hotspots of evolution with unique, untouched nature. But the settlement of humans in places like the Canary Islands, Tonga and the Azores led to widespread impacts, including deforestation, overhunting and the introduction of invasive species. As a result, numerous bird species were wiped out. While the extinction of many birds has been documented since the year 1500, our knowledge of the fate of species before that time is based on fossils. Such fossils are rarely available because small bird bones decompose over time. As a result, the true extent of global extinction caused by humans is difficult to quantify.
The international research team used statistical models for the first time to estimate the “true” number of previously unknown bird species that have been extinct by humans since the Late Pleistocene, around 130,000 years ago. The study team based its models on information about known extinctions and the extent of research within focal regions. Because: The less research has been carried out in a region, the more incomplete the fossil evidence is, and the greater the number of extinct species that remain undiscovered.
“So far we knew from observations and fossils that 640 bird species have become extinct due to humans - 90 percent of them on islands,” says Prof. Dr. Manuel Steinbauer. The spectrum ranges from the iconic dodo in Mauritius to the great auk in the North Atlantic to the lesser-known St. Helena giant hop. “However, based on the model results, we estimate that the actual number is slightly more than twice as high,” explains the Bayreuth ecologist. He and his colleagues speak of 1,430 extinct species, which corresponds to around 11% of all bird species, so that only around 11,000 remain today.
The scientists believe their study has uncovered the largest human-caused extinction of vertebrates in history. In addition to the effects of global sea travel in the 14th century, major waves of extinction were caused primarily by the arrival of humans on the Pacific and Atlantic islands three thousand years ago.
Dr. Rob Cooke, an ecological modeler at the UK Center for Ecology & Hydrology, led the study, which has now been published in the renowned journal Nature Communications. He says: "Our study demonstrates there has been a far higher human impact on avian diversity than previously recognised. Even small human populations have rapidly devastated bird populations via habitat degradation, overexploitation and the introduction of rats, pigs and dogs that raided nests of birds and competed with them for food. We show that many species became extinct before written records and left no trace, lost from history.”"
Prof. Dr. Manuel Steinbauer from the University of Bayreuth, one of the study's co-authors, emphasizes the importance of fossils for understanding extinction processes. “These allow us to look into the past. Unfortunately, it turns out that the arrival of humans on islands, regardless of cultural or technological background, has had a fatal impact on ecological systems. “In view of the current extinction of species, it is now important for us to understand how the loss of a species and the associated loss of an ecological function affects the interaction in ecological systems.”
And bird extinction continues: The researchers point to the current, ongoing extinction that began in the middle of the 18th century. Since then, in addition to increased deforestation and the spread of invasive species, birds have also faced human-caused threats from climate change, intensive agriculture and pollution. Data from the International Union for Conservation of Nature (IUCN) suggests that we will lose up to 700 more bird species over the next hundred years. This can have fatal consequences: the extinction of one species always impacts the entire ecosystems,” warns Steinbauer. “Birds, for instance, may have key functions such as seed dispersal, insect population control or plant pollination “
The study included scientists from the University of Gothenburg, the Gothenburg Global Biodiversity Center, the Center for Ecological Research and Forestry Applications (CREAF), Uppsala University in Sweden, University College London, the Zoological Society of London (ZSL), the Royal Botanic Gardens Kew, the University of Oxford and the University of Bayreuth.
Contact for scientific information:
Prof. Dr. Manuel Steinbauer
Holder of the professorship for sports ecology
University of Bayreuth
Tel.: +49 (0) 921 / 55-5834
Email: steinbauer@uni-bayreuth.de
Original publication:
Cooke, R., Sayol, F., Andermann, T. et al. Undiscovered bird extinctions obscure the true magnitude of human-driven extinction waves. Nat Commun 14, 8116 (2023). https://doi.org/10.1038/s41467-023-43445-2
